Deliming and deswelling hides with beet sugar molasses waste liquor extract



Patented June 12 195 1 DELIMING AND DESWELLING HIDES WITH BEET SUGAR MOLASSES WASTE LIQUOR EXTRACT Felix Heinemann, Philadelphia, Pa.

No Drawing. Application June 23, 1948, Serial No. 34,845

3-Claims. (cm-94.17)

1 My invention relates to a process for the deliming and deswelling or bating of skins and hides which have previously been unhaired or depilated in the slack lime pit or the like. Good bating is of very great and even decisive importance in the production of fine grain leather. To achieve this purpose it is necessary to transform the lime of the skin or hide into neutral watersoluble calcium salts and thus to facilitate removal of the lime. In addition to lime removal,

the elimination or weakening of the elastic fibers,

the degradation or disintegration of keratose, and a certain loosening or disaggregation of collagen by means of protein-splitting enzymes are generally considered among the essential effects of the bating process. It is for this reason that bating materials containing protein-splitting enzymes are used to a great extent in the leather industry.

The customary methods for the deswelling and deliming of skins and hides, however, are relatively primitive. In practice deliming and deswelling are carried out either in an acid or in an alkaline medium. Working in the acid range is advantageous because the lime will then safely be transformed into neutral water-soluble compounds. and skins in acid solutions can be successfully carried out only under accurate control. It is necessary not to overstep the point at which all the lime is removed while the hide or skin is not yet swelled by the acid. Moreover one has to avoid putting the depilated or smoothed'skin or hide, which has a pH value of about 12, into a solution of a very difierent pH value. Otherwise the quality of the leather to be manufactured will suffer, particularly in the grain layer. For this reason it is general practice to maintain the hydrogen ion concentration of the bating bath as low as possible. Organic acids of low dissociation value, such as formic acid, acetic acid, butyric acid, lactic acid, and the like, are therefore preferably employed, and such acid is added in small batches only to the deliming bath. Modern enzyme bates reach optimum efficiency in the alkaline range, and maximum disintegration of keratose and elastin is considered tooccur between pH '7 and 8. Ammonium salts which are added to activate the enzymes make it possible to delime and deswell the unhaired skins or hides in the alkaline range. Even in this case, however, the conditions cannot be 'closely controlled and will often not even approach optimum conditions, particularly since the pH value of. the solution is to a large extent dependent on the But deliming and deswelling of hidesamount of ammonia escaping from this solution,

It isan object of this invention to delime and deswell skins and hides under exact control and in such a manner that a leather of excellent quality and with very fine and tender grain is obtained.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

With these objects in view, my invention utilizes bufier mixtures of weak acids and bases which have a dissociation constant smaller than that of ammonia for the deswelling and deliming of unhaired skins and hides.

If acids of a very low dissociation constant are employed for this purpose, the bufier mixtures obtained from suitable proportions ofbase and acid will beof low actual but high potential acidity. Such mixtures are real safety-bates which even in most simple and uncontrolled application will allow a riskless deswelling and deliming of skins and hides in the acid range. When the acids are neutralized by the lime, the weak bases present impart to the hate liquid a neutral to weakly alkaline reaction which is best suited for the action of proteolytic, particularly tryptic enzymes. A buffer mixture of the indicated kind which has a specific hydrogen ion concentration is very constant and stable against forces causing a change in the pH value.

A mixture of this kind can, for example, be obtained by mixing 5 parts by weight, each, of

formic acid and of lactic acid with 15-20 parts by weight of commercial tobacco extract. The mixture thus obtained has a pH value of about 4.7. Instead of tobacco extract, nicotine or the accessory-alkaloids of nicotine, or both, or weak organic bases of other origin can be employed.

I have found further on that mixtures of this kind which are eminently suited for attaining the object of my invention are already present in the waste liquors or slops which are obtained in the desugaring of beet molasses. Such mixtures of weak nitrogen bases and'weak organic acids excellently suitable for deswelling and deliming unhaired hides and skins can be obtained from said waste liquors or slops in a very simple and cheap manner. Waste liquors from beet sugar molasses desugaring processes, either from processes for recovering sugar itself, e. g. by the Steffens desugaring process, or from the production of alcohol from these molasses by fermentation of the sugar contained therein, or from the cultivation of yeast by means of these molasses, are equally suitable for recovering base-acid mixtures of the indicated type well suited for my process. o J

These waste liquors or slops contain numerous vegetable bases, such as xanthine, hypoxanthine, guanidine and the like, most of them in very small amounts only. Betaine, however, the most characteristic basic constituent of these slops is contained therein in considerable amounts. This compound has basic as well as acid properties. a feature most favorable for the purpose in mind. The basic character is prevalent. Mere acid constituents of said slops are mainly: formic acid, acetic acid, butyric acid, propionic acid, valeric acid and lactic acid, and decomposition products of acidic character from pectin and sugar.

The major portion of the acidic substances in the beet molasses slop is bound to potassium oxide, while a small portion is bound to sodium oxide, lime and magnesium oxide. removed as far as feasible before use. 7

An excellent deliming and deswelling preparation can, for example, be obtained in the following manner: Waste liquors from the production of sugar, alcohol, oryeast from beet sugar molasses are first concentrated to a s'p. gr. of about 1.4, for example by means of multiple effect evaporators. 2,650 lbs. of the concentrated slop are mixed with an amount of sulfuric acid sufficient to transform all of the ash content into sulfates. Depending on the amount of ashes present about 290-3301bs..of sulfuric acid of 66 Be. are required for this purpose. This amount of concentrated acid is first diluted by the addition of 200-220 liters of water. After cooling, the thus diluted sulfuric acid is slowly added to the slop while constantly stirring. Overheating by this addition has to be avoided. During this treatment the slop becomes rather viscous while large amounts of sulfates and of sludge-like components are precipitated. The resulting mixture is well cooled to cause crystallization and precipitation of further amounts of sulfates. The salt-containing Sludge is separated and removed from the liquid by depositing or centrifuging. 220 lbs. of the concentrated slop employed render about 110 lbs. of liquid and about 155 lbs. of aqueous sludge. This sludge may be utilized, if desired, as a potash manure. The major part of the salts contained in this sludge are inorganic. At least 50% of the organic components of the beet. sugar molasses slop or waste liquor are contained in the remaining liquid which represents the bating mixture, and are utilized therein. Sewage disposal, which is a very serious problem in sugar, fermentation and yeast industries, is thus substantially facilitated.

The recovered liquid .contains about 3.5% of nitrogen, about 12-15% of betaine. and about 12-15% of acids calculated on the basis of lactic acid. Infact, however, it is not only lactic acid which is contained in this liquid, but a mixture of numerous weak organic acids, part of which were already contained in the beet and another part of which is formed during the recovery of sugar from beets by decomposition of protein, pectin, orsugar. All the acids found in the analysis of molasses are also contained in the hating These are liquid produced. Acidic compounds which are formed by decomposition of sugar have proved to be particularly valuable in the formation of a fine grain in leather. This can be demonstrated by trying to brighten the somewhat dark color of the liquid obtained by treating it with active carbon. The dark, caramel-like acidic components are removed and the acid content is reduced, but the grain of the unhaired skin is not as tender, soft and smooth as it is when using the bate liquid without carbon treatment.

Though said sugar decomposition compounds which are in an amorphous state cannot be exactly defined and guesses only are possible as to the cause of their efficiency, it appears probable that these compounds are acids of weak dissociation and have a rather high equivalent weight relative to that of formic acid, acetic acid, or the. like. This causes a substantial increase in the buffering effect of the betaine.

The liquid product obtained by the process described above thus represents a mixture of weakly and very weakly dissociated organic acids and vegetable-bases, particularly betaine. The buffer mixture thus formed has proved to be extremely useful as a hating bath in the deliming and deswelling of unhaired or smoothed skins and hides. After the acid of this bating bath is neutralized by the lime present in the hide or skin, the. bath becomes approximately neutral to weakly alkaline, due to the presence of the weak bases, particularly the betaine. The condition is bestsuited forthe use of tryptic enzymes. The product to be employed according to my present invention thus behaves similar to this respect to the dung bates formerly used. No acidor basic ions other than organic ones, and particularly no Cl or Naions, which have a distinct and different effect on the swelling of the skins and hides, are present in my buffer mixture.

The bating of unhaired skins and hides by means of the liquid obtained by the above described treatment of Waste liquor or slop fromthe desugarin g of beet sugar molasses can be carried out, for example, as follows:

The washed unhaired skins or hides are first treated for a, short period of time with water of about 105 F. About 3.5-4.5 lbs. of the concentrated bate liquid obtained as described above are then added to about 220 lbs. of the unhaired skins or hides during 15-20 minutes, preferably in two equal portions. It is advisable not to allow the temperature of the bath to decrease too much, as the elfect is substantially reduced if the temperature drops below F. A temperature of about 10.0-l05 F. is most favorable. After a treatment of 1-2 hours the skins and hides will be free. of lime. The smoothed skin or hide is thereafter advantageously treated with one of thewell known enzyme bates of the commerce such as the .tryptic enzyme Oropon of Rohm & Haas, otherwise employed in the deliming of skins. by ammonium salts. In the present case, however, an amount of enzyme of only 40-50% of that customarily used is required. The skins and hides fall easily quickly and completely while the grain layer is very well preserved and is particularly smooth and tender. Dirt and hairs are very easily removed. If desired, the anzyme treatment can be combined with the treatment with my buffer mixture.

The new process works very safely and never damages the skin or hide. It effects deliming and deswelling in the acid range, ensuring these effects to be complete and perfect. The conditions prevailing after neutralization of the lime are such that the tryptic or other proteolytic enzymes will work to best advantage. It is for this reason that 50-60% of these enzymes can besaved.

If desired, the new bating liquid can either in its original state or after further concentration to syrupy consistency be adsorbed .or absorbed onfporous inert solid carriers, such as saw-dust or the like, so that a solid'material is obtained which can be handled and shipped more easily.

In cases where beet sugar molasses are subjected to desugaring or similar treatment in admixing with cane sugar molasses or blackstrap as for instance in certain processes for the cultivation of yeast by means of molasses, the waste liquors or slops obtained can also be utilized for the production of the new bate. For this purpose the waste liquor or the yeast cultivation is treated in a manner corresponding to that described above for the treatment of slop from the desugaring of beet sugar molasses. The liquid thus obtained which contains a smaller percentage of organic nitrogen because of the, absence of nitrogen in. or the very low nitrogen content of cane sugar molasses, is then admixed with a sufficient amount of tobacco extract or the like, to give the desired pH value of about 4.7. The waste liquors obtained in the desugaring of cane sugar or blackstrap molasses only, e. g. in their fermentation for the production of alcohol, can also be utilized in the production of the new bate liquid. In this case, however, a correspondingly greater amount of tobacco extract or other weak organic bases has to be added to obtain a bufier liquid of the desired pH value.

Where the waste liquor obtained in desugaring beet sugar molasses by recovering the sugar as such, for instance the so-called Stefiens filtrate from the Stefiens process, is utilized for the production and recovery of glutamic acid or monosodium glutamate, the filtrate obtained after crystallization and separation of the glutamic acid or its monosodium salt can still be utilized for the production of my new bate, since it still contains all of the betaine of the original beet sugar molasses slop, and because it is this nitrogen base which is of main importance for my new bating material. The fact that the material thus obtained does not contain any glutamic acid is of no importance, just as it has no bearing on the utilization of the waste liquor from yeast cultivation by means of beet sugar molasses. The amino acids contained in the beet sugar molasses are utilized by the growing yeast for building its own body substance while the betaine remains unattacked. If desired or required, small amounts of tobacco extract, or the like, can be added to the bate liquid also in this case in order to get to the desired pH value. The deliming operation employed in the recovery of glutamic acid from Stefiens filtrate, i. e. the carbonation with lime kiln gases or the like, can also be used in the treatment of the original slops from the desugaring of beet sugar molasses.

Any kind of enzymes useful in the bating of skins and hides, such as those used in known bating processes, particularly proteolytic enzymes of animal or vegetal origin, can also be employed 6 in my above described process, the particular choice of the enzymes to be used not forming part of my present invention.

The fact that waste products of other industries can be utilized as the starting material in the production of the liquid to be used for deliming and deswelling skins and hides by my new process contributes substantially to the low costs of this process.

I claim:

1. The deliming and deswelling of unhaired hides and skins with a composition essentially consisting of an aqueous mixture of the amphoteric betaine, the organic bases: Xanthine, hypo- Xanthine, and guanidine, and the weak organic acids: formic, acetic, butyrio, propionic, valeric, and lactic acid, said mixture being directly obtained from beet sugar molasses waste liquor.

2. The deliming and deswelling of unhaired hides and skins with a composition essentially consisting of an aqueous mixture of the Weak organic acids: formic, acetic, propionic, butyrio, valeric, and lactic acid, and acidic decomposition products of sugar, pectin and protein, the amphoteric compound betaine, and minor amounts of the organic bases: xanthine, hypoxanthine, and guanidine, said mixture being directly obtained from beet sugar molasses waste liquor.

3. The deliming and deswelling of hides and skins in the manner indicated in claim 2, said aqueous mixture being absorbed by a solid absorbent.

FELIX HEINEMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 87,202 Robertson Feb. 23, 1869 638,828 Wood Dec. 12, 1899 1,763,319 Orthmann June 10, 1930 2,033,163 Wallerstein Mar. 19, 1936 2,192,228 Hill Mar. 5, 1940 2,266,448 Troskin Dec. 16, 1941 2,375,164 Bennett May 1, 1945 2,413,164 Shafor Jan. 7, 1947 2,448,051 Reich Aug. 31, 1948 OTHER REFERENCES "Practical Tanning by Rogers, pub. 1922, page 116.

The Rationale of Eating by J. T. Wood. Reprinted from Leather Industries Sept. 1898.

Ser. No. 402,440, Coutor (A. P. C.), published June 1, 1943. 

1. THE DELIMING AND DESWELLING OF UNHAIRED HIDES AND SKINS WITH A COMPOSITION ESSENTIALLY CONSISTING OF AN AQUEOUS MIXTURE OF THE AMPHOTERIC BETAINE, THE ORGANIC BASES: XANTHINE, HYPOZANTHINE, AND GUANIDINE, AND THE WEAK ORGANIC ACIDS: FORMIC, ACETIC, BUTYRIC, PROPIONIC, VALERIC, AND LACTIC ACID, SAID MIXTURE BEING DIRECTLY OBTAINED FROM BEET SUGAR MOLASSES WASTE LIQUID. 